[claudiusd]

You basically nailed the problem: the generally-accepted status quo is based on flimsy evidence. Our metabolism is complicated and it will likely take decades before we fully understand it, not to mention that different people process calories differently.

Luckily, it's very easy to detect when your diet is having a negative impact on your health and you have time to make changes before heart disease or type 2 diabetes strikes. There's no excuse for not keeping track of your weight and not getting regular blood work to look for risk factors. When these risk factors emerge, very simple changes like eating more vegetables and spending more time walking can be enough to reverse them. Easier said than done of course, but we do have reliable science that shows this.